1. Field of the Invention
The present invention relates to an apparatus and method for determining a start up of a sensorless motor, and more particularly to an apparatus and method for determining a start-up of a sensorless motor with no sensor attached thereto, wherein, even when position estimation of the motor fails, a determination is made as to whether the motor has been normally started up, using a velocity of the motor, a voltage and current applied to the motor, etc., when a predetermined time has elapsed after the motor was started up.
2. Description of the Related Art
FIG. 1 is a block diagram showing the construction of a general inverter driver with a motor.
An inverter is an electric power apparatus for varying a frequency in order to drive a motor at any velocity. The inverter generally includes, as shown in FIG. 1, a power module which is modularized with a power device, a gate circuit and an overcurrent protection circuit.
Meanwhile, an inverter induction machine generally employs a voltage/frequency (V/F) control method of an open loop type with no position and velocity estimation due to characteristics thereof. The overcurrent protection circuit which is arranged in the power device is used as a protection module for the inverter induction machine.
However, since the overcurrent protection circuit aims to protect the power device, it may operate at a very high operating level at which relatively high current flows to the circuit, resulting in damage to the motor.
That is, higher current than a withstand voltage characteristic of the motor may flow in the motor even though it is below the operating level of the protection circuit. In such a case, the motor may be damaged. Particularly, when the motor fails to be started up, it is difficult to determine the start-up failure without performing the velocity estimation because of characteristics of the motor.
In order to resolve the above problem, the operating level of the overcurrent protection circuit may be lowered below a predetermined value. In this case, however, even when current flowing in the motor is normal, it may be determined to be higher than the operating level of the protection circuit, thereby causing the operation of the power device to be stopped.
Thus, there is a need for an additional protection circuit for protecting not the power device, but the motor.
In the case where the above motor is a sensorless motor with no sensor attached thereto, a voltage is applied in an open loop state using the V/F control method under the condition that the position and velocity thereof are not detected. For this reason, even though the motor fails to be started up, it may not be possible to determine whether the amount of current flowing in the motor is excessive or not, which may lead to damage to the motor.